This invention relates to an arrangement for the forming of form pieces by point rolling of an active surface of a forming tool along the formed surface.
A number of arrangements are known for the forming of form pieces in the direction of the axis of the form piece, wherein an additional movement of the forming tool is used in order to utilize the forming forces more effectively or in order to reduce the forming force. Different kinds of these arrangements, whether they are riveting machines or presses with rocking dies, use different principles of movement of the active surface of the tool with respect to the formed surface.
One of these principles uses a rolling motion of the tool along a circle the center of which lies on the axis of the formed surface, whereby the place of contact of the tool with the formed surface is half the meridian of the formed surface. The direction of flow of the formed material is not the most advantageous in this case for many forming operations due to the tangential character of movement of the tool along the formed surface.
Another kind of arrangement uses a principle of movement of the tool wherein its axis describes a hypocycloid curve, whereby the center of the active surface of the tool is coincident with the center of the formed surface within the whole forming interval. The place of contact of the tool with the formed surface is a rolling curve, the length of which varies from zero to a maximum. The movement of the tool along the formed surface has a radial-tangential character.
Other modifications of these arrangements operate according to the same principle, with the difference that the kinematic coupling is not stable-hypocycloidal, but is free; the movement is composed of two independent movements, the consequence of which is the possibility of variation of the ratio of the radial and tangential components of the movement of the tool.
A drawback of arrangements of this kind is that the individual rolling cycles proceed along the surface of the formed surface, the consequence of which is a certain lateral action on the piece being formed; this can be unwelcome in some cases. A drawback is also that the support of the tool transmitting the forming force is accomplished by a spherical surface, i.e. with the most unfavorable sliding friction. The most convenient of known arrangements are those wherein the additional movement of the tool securing the forming by rolling is based on the principle of a reciprocative point rolling of the active surface of the tool along the meridian of the formed surface. The forming of mostly rotational surfaces by reciprocative point rolling is secured by superposition of a reciprocative rolling upon a rotation of the plane of rolling. An advantage of this principle is the theoretical action of the tool on the formed surface in a point in the course of the whole forming interval, thereby achieving the highest intensity of forming in small volumes, and furthermore the elimination of lateral forces on the form piece within one cycle of the reciprocative rolling motion. Known arrangements for forming by reciprocative point rolling have a lateral drive of the reciprocative movement by a second shaft, with large kinematic couplings, resulting in undesirable larger lateral dimensions of the arrangement.